Help with parametric equations

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SUMMARY

The discussion focuses on finding parametric equations for the semicircle defined by the equation x² + y² = a², specifically for the upper half where y > 0. The initial approach involves using the standard parametrization x = a cos(t) and y = a sin(t) for 0 ≤ t ≤ π. The user correctly identifies the derivative dy/dx as -x/sqrt(a² - x²) and seeks guidance on how to express x and y in terms of the slope parameter t. The solution involves expressing x and y as functions of the slope parameter to derive the parametric equations.

PREREQUISITES
  • Understanding of parametric equations and their applications
  • Knowledge of calculus, specifically derivatives and slopes
  • Familiarity with the equation of a circle and its geometric properties
  • Basic algebraic manipulation skills to solve for variables
NEXT STEPS
  • Study the derivation of parametric equations for different geometric shapes
  • Learn how to manipulate derivatives to express variables in terms of parameters
  • Explore the relationship between slopes and parametric representations in calculus
  • Investigate applications of parametric equations in physics and engineering contexts
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Students studying calculus, particularly those focusing on parametric equations and their applications in geometry. Additionally, this discussion is beneficial for educators seeking to enhance their teaching methods in mathematical concepts related to curves.

miglo
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Homework Statement


find parametric equations for the semicircle x^2+y^2=a^2, y>0
using as parameter the slope t=dy/dx of the tangent to the curve at (x,y)


Homework Equations





The Attempt at a Solution


well i know that to parametrize a circle i would use x=acost and y=asint for 0<=t<=2pi
so i guess if i just want the top half i would use 0<=t<=pi ? but I am not sure how to use the derivative of y=sqrt(a^2-x^2) to parametrize the curve
i went ahead and found dy/dx to be 1/2(a^2-x^2)^(-1/2)*-2x or -x/sqrt(a^2-x^2)
i don't know what to do next...
 
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Your expression for the slope is correct, but it will probably help you to reduce it a bit more (hint what is a2-x2?).

If we call the slope for s (our parameter), can you then express x as a function of s and y? If so, perhaps you can use this relation to get rid of x in another equation so it ends up only relating y and s, thus allowing you to find y as a function of s. Repeat with y as a function of s and x to get a parameterization for x.
 

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